Recently, in an IC card, a cell phone, and a portable terminal device or the like, there is an increasing demand for a thinner, smaller, and lighter structure of an electronic circuit device formed of a semiconductor element or a composite of a semiconductor element and an electronic component. To realize such small and thin design, in particular, an electronic circuit device without using a die pad or a wiring substrate is proposed.
FIG. 10 is a sectional view of a conventional electronic circuit device that does not use a support substrate such as a wiring substrate disclosed in Unexamined Japanese Patent Publication No. 2001-217338. In this electronic circuit device, a conductive path 50, a semiconductor element 51, and a chip type electronic component 54 are buried in an insulating resin 56. The semiconductor element 51 is fixed to a conductive path 50B of the conductive path 50 by means of a conductive paste 52 such as silver paste. Electrode pads (not shown) of the semiconductor element 51 are connected to conductive paths 50A, 50C of the conductive path 50 by means of a thin metal wire 53. Electrodes of the chip type electronic component 54 are connected to conductive paths 50C, 50D of the conductive path 50 by using a brazing material 55. A part of the conductive path 50 in a thickness direction is buried in the insulating resin 56, and the other side is exposed from the insulating resin 56.
The insulating resin 56 is, for example, a thermosetting resin such as epoxy resin, or a thermoplastic resin such as polyimide resin, and is processed into a shape as shown in the drawing by mold forming by using a die. The conductive path 50 is a conductive film mainly made of copper or aluminum, or an alloy foil of iron-nickel or the like.
This electronic circuit device is manufactured in the following process. First, in a thickness direction of conductive foil, division grooves are formed to a depth greater than the thickness of the shape finally becoming conductive films 50A, 50B, 50C, 50D individually. Next, in a region to become conductive path 50B, a semiconductor element 51 is die-bonded, and regions to become conductive paths 50A, 50C and electrode pads are connected by a metal thin wire 53. A chip type electronic component 54 is mounted by soldering or the like in regions to become conductive paths 50C, 50D. Later, the parts are molded by an insulating resin 56. Further, the conductive paths are polished and division grooves are exposed, so that an electronic circuit device having mutually separate conductive paths 50A, 50B, 50C, 50D is obtained.
Further, an electronic circuit device intended to not only become thin but also prevent cracks of the package in solder reflow is disclosed in Unexamined Japanese Patent Publication No. H7-321139.
FIG. 11 is a sectional view of this electronic circuit device. In this electronic circuit device, electrode pads (not shown) of a semiconductor element 61 and leads 62 are connected by a bonding wire 63 of thin metal wire, and the parts are molded by an insulating resin 64 except for parts of leads 62. Since the leads 62 and semiconductor element 61 are supported by the insulating resin 64, a support substrate is not needed, and as compared with the conventional electronic circuit device using a lead frame, not only is the thickness reduced, but also cracks are less likely to occur even when heat is applied in solder reflow.
This electronic circuit device is manufactured in the following process. First, a support stand having a recess for fixing the semiconductor element 61 is prepared. Next, in the recess of the support stand, the semiconductor element 61 and a lead frame are disposed. A die pad is not provided at the lead frame, and only leads 62 are provided. The semiconductor element 61 is temporarily fixed to the support stand by vacuum attraction. Electrode pads (not shown) of semiconductor element 61 and leads 62 are connected by a bonding wire 63. In this state, the semiconductor element 61 held by the lead frame and bonding wire 63 is dismounted from the support stand, and is placed in a molding die, and is molded with resin. After that, from the molded structure, the lead frame is cut off, and the leading ends of the leads 62 are folded outward, so that the electronic circuit device shown in FIG. 11 is obtained.
According to the electronic circuit device explained in JP 2001-217338, since the conductive paths are supported by the insulating resin, the support substrate is not needed in the final state. Therefore, as compared with the conventional electronic circuit device using the lead frame, a thinner electronic circuit device is realized. However, since the semiconductor element is fixed to the surface of conductive paths by solder or the like, strain due to a difference in coefficient of thermal expansion occurs, and expansion or cracks may be caused. Besides, to realize an electronic circuit device, it is required to polish the conductive foil until division grooves are exposed, and this step is relatively complicated, which makes it hard to reduce the cost.
In the electronic circuit device explained in JP H7-321139, the semiconductor element is not bonded to a die pad, but is buried in the insulating resin. Therefore, if the electronic circuit device is exposed to heat when it is mounted on the circuit board, cracks can be prevented.
In this electronic circuit device, however, since the leads are exposed from the side of the insulating resin used as molding resin, and the external connection terminals are folded in structure, the mounting surface area of the circuit board cannot be decreased. In this method, meanwhile, nothing is taught about the mounting structure of the plurality of semiconductor elements, a composite component of the semiconductor element, a passive component or the like.